Technical Field
The present disclosure relates to a control method of an energy management and more particularly, to an energy management system which is capable of reflecting a state of each energy storage system in the energy management system.
Description of the Related Art
With advance in industries, as demands for power are increasing and a difference in load between day and night and a difference in power consumption between seasons and between holidays are gradually increasing, deterioration of a load factor is deepening day by day.
For this reason, in recent years, a variety of load management techniques have been rapidly developed to utilize surplus power to reduce a peak load. A battery energy storage system is representative of such load management techniques.
The battery energy storage system saves surplus power at night or surplus power from wind power stations or solar power stations and supplies power to loads by discharging the saved surplus power at the time of peak load or system fault, thereby achieving peak load reduction and load levelling.
In particular, such a battery energy storage system can also be used in a smart grid which is being recently highlighted with appearance of a variety of renewable energy sources.
The battery energy storage system can be used for load levelling, peaks including, frequency regulation, emergency generator and so on for grid stabilization.
The load levelling, peaks including and frequency regulation means that the system operates in a grid-connection type and the emergency generator is used as a micro-grid including no main grid or an emergency source against black-out.
Such a battery energy storage system may include an electrical or chemical battery, an inverter, a transformer and the like. For a high-power system, a number of battery energy storage systems may be connected in parallel.
In this case, a controller for controlling the battery energy storage systems divides an output command from an upper control unit by the number of battery energy storage systems and transmits energy storage system output commands including the same value to the battery energy storage systems, respectively.
At this time, the controller can generate the output commands based on a state of charge (SOC) of a battery in each battery energy storage system.
The SOC of each battery has to fall within an allowable range. If there exists a battery including a SOC out of the allowable range, the controller can stop a power output operation based on an output command of an energy storage system including the battery.
However, if an operation of one of batteries in a plurality of energy storage systems is stopped, there is a problem that the total sum of power output from the remaining energy storage systems except the energy storage system including the battery is smaller than the sum of output commands transmitted from the controller.
This is because the output commands are generated based on an average of sums of SOCs of individual batteries with no consideration of individual batteries.